Electronic Package With Direct Cooling Of Active Electronic Components

ABSTRACT

A cooling assembly includes a package with one or more dies cooled by direct cooling. The cooled package includes one or more dies with active electronic components. A coolant port allows a coolant to enter the package and directly cool the active electronic components of the dies.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electronic packaging.

2. Related Art

An electronic package can house one or more dies, however, activeelectronic components on a die generate heat during operation. Such heatneeds to be removed from a package to avoid overheating and reducedperformance. The need for thermal management becomes greater as thenumber of dies desired to be housed in a single package increases andthe operating load of each die increases. For example, thermalmanagement is a significant concern for high-density packages whichinclude multiple dies in a relatively small area. Further, dies arecontinually expected to include greater numbers of active electroniccomponents such as transistors, and to operate at ever greater clockrates and input/output (IO) speeds. The need to dissipate heat is evenmore important in high-density packages with dies carrying outsignificant processing operations at high clock rates.

Two conventional approaches developed by IBM Corp. and NEC Corp. addressthe problem of heat dissipation on a package level basis inhigh-performance computers. The IBM approach uses a thermal conductionmodule (TCM) to cool a high-density flip chip multi-chip module (MCM).This approach however is limited to back side cooling. Active surfacesof dies which are flip-chip bonded only face a substrate and are notdirectly cooled. Uneven thermal gradients and hots spots can still occuron active die surfaces. The NEC approach provides liquid cooling modules(LCMs). However, these LCMs only contact the exterior of an entirepackage. In this case too, cooling the package exterior does notdirectly cool active surfaces of flip-chip bonded dies in a package.Uneven thermal gradients and hot spots can still arise across the dies.See, e.g., Advanced Electronic Packaging with Emphasis on MultichipModules, edited by W. Brown, Chapter 13, “Mainframe Packaging: TheThermal Conduction Module,” published by I.E.E.E. Press, Piscataway,N.J., 1999, pp. 492-565. More effective cooling of active electroniccomponents within an electronic package is needed.

BRIEF SUMMARY OF THE INVENTION

The present invention provides direct cooling of active electroniccomponents within an electronic package. A cooled package includes oneor more dies. Each die is directly cooled on one or more sides by acoolant present within the cooled package. In this way, heat generatedby active electronic components on one or more surfaces of a die istransferred away from the active electronic components. Such directcooling of die surfaces in an electronic package according to thepresent invention minimizes temperature variation across each die andreduces electrical parameter variation. Hence, the uniformity of outputsignal characteristics such as rise time and pin-to-pin skew isimproved. Hot spots on a die surface are reduced or eliminated, allowingthe operating temperature range of a die to be increased.

In one embodiment, a cooled package includes a housing that encloses acavity. The housing has at least one coolant port that allows a coolantto circulate within the cavity. Each die is mounted on a substratewithin an enclosed and sealed cavity in which coolant is circulated. Inone example, one die is mounted within the cavity of the housing. Inanother example, a plurality of dies are mounted within the cavity ofthe housing. In another example, a high-density cooled package isprovided in which an array of densely packed dies are arranged withinthe cavity of the housing. In another example, a high-density cooledpackage includes an array of densely packed dies mounted such that diesurfaces with active electronic components face a substrate within thecavity of the housing.

In one embodiment, a housing of a cooled package includes top and bottomsubstrates coupled by a seal. A cooling system is coupled to a coolantcirculation system to provide liquid and/or gas coolant into and out ofone or more coolant ports in the housing. In one arrangement, thehousing includes two coolant ports. For example, two ports such asone-way flow valves can be provided in an O-ring seal coupling the topand bottom substrates. One port passes coolant into the cavity and theother port passes coolant out of the cavity. In this way, heat istransferred directly away from the active surfaces of the dies.

According to a further feature, one or more dies include compliantinterconnects coupled to at least one substrate. Such compliantinterconnects allow coolant to circulate around all surfaces of the dieswithin the cavity while maintaining effective structural and electricalcontact between each die and the substrate. In preferred embodiments ofthe present invention, the compliant interconnects are spring contactswhich couple a die to a bottom substrate. Dies can be soldered to thespring contacts or held with the aid of alignment posts in a socketconfiguration. The spring contacts provide a flexible, resilientstand-off. Liquid or gas coolant flows between the substrate and one ormore sides of each die. The coolant makes direct contact with each diesurface including the active die surface provide uniform cooling evenfor high-power applications. Such spring contacts allow coolantcirculation and heat transfer away from active surfaces of dies evenwhen the dies are mounted to face a substrate within the cavity of ahousing.

According to a further feature, non-contacting compliant interconnectsare also provided on a die surface. A non-contacting compliantinterconnect can be any type of compliant interconnect such as a spring.These non-contacting compliant interconnects do not contact a substrate,but serve to direct heat away from areas of the die surface. Thisfurther improves cooling of die(s) in a cooled package according to thepresent invention.

In one embodiment, a cooled package includes one or more dies mounted ina stacked die arrangement. In this arrangement, one or more dies areflip-chip bonded to a top substrate. The top substrate is then coupledby compliant interconnects to a bottom substrate.

In one embodiment of a cooled package according to the presentinvention, contacts are provided on a cooled package to electricallyconnect each die with external components. In one embodiment, contactsare provided at a peripheral edge of the bottom substrate. In anotherembodiment, contacts are provided at a top substrate. Electricalconnections can be coupled to the contacts. According to a furtherfeature, additional electrical connections run through a cooled packagedirectly between top and bottom substrates.

An advantage of the present invention is that embodiments of the presentinvention can include one or more dies which carry out high-powerprocessing operations without reaching an overheating condition thatdegrades signal quality to an unacceptable level. A further advantage ofa cooled high-density package embodiment according to the presentinvention is that it can compactly house a number of dies. In a compactembodiment, the size of the cavity within the package (also called thepackaged component area) is only slightly larger than the footprint ofthe dies themselves.

One additional advantage of an electronic package with direct coolingaccording to the present invention is it is easy to disassemble formaintenance and repair. Another advantage of an electronic package withdirect cooling according to the present invention is that it isinexpensive to assemble. Another advantage is that in certainembodiments electrical interconnects can be made to both the top andbottom of the package.

Further, in another embodiment, an electronic package according to thepresent invention includes a cooling member and a cooled package withone or more heat radiators such as cooling fins. The cooled packageincludes a housing that encloses a cavity. A coolant fills the cavity.One or more dies are mounted through compliant interconnects to asubstrate within the cavity and are directly cooled by surroundingcoolant. In this embodiment, however, heat is transferred away from thecoolant by one or more heat radiators to the cooling member.

According to another embodiment, a method for direct cooling of activeelectronic components is provided. The method includes attaching activeelectronic components to a substrate with an active surface facing thesubstrate, sealing the attached active electronic components in apackage, and circulating coolant through the package to directly contactthe active surfaces of the active electronic components.

Further features and advantages of the present invention, as well as thestructure and operation of various embodiments of the present invention,are described in detail below with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention. In the accompanying drawings:

FIG. 1 is a flowchart of a routine for direct cooling of activeelectronic components according to an embodiment of the presentinvention.

FIG. 2 is a diagram of a cooling assembly and cooled package accordingto an embodiment of the present invention.

FIG. 3A is a diagram of a cooling assembly and cooled package accordingto an embodiment of the present invention.

FIG. 3B is an example plot that illustrates the principle of how aliquid coolant generally remains at a constant temperature throughout aboiling range during operation of the cooling assembly shown in FIG. 3A.

FIG. 3C is a diagram of a cooled package according to an embodiment ofthe present invention.

FIG. 4A is a diagram of a high-density cooled package with outputcontacts at the edge of a substrate according to an embodiment of thepresent invention.

FIG. 4B is a diagram that shows dies mounted in a stacked diearrangement according to an embodiment of the present invention.

FIG. 4C is a diagram that illustrates non-contacting compliantinterconnects provided on a die surface according to a further featureof the present invention.

FIG. 5 is a diagram of a high-density cooled package with electricalconnection through a housing cavity and output contacts on a top ceramicsubstrate according to an embodiment of the present invention.

FIG. 6 is a diagram of a high-density package illustrating dies attachedin a socket configuration according to an embodiment of the presentinvention.

FIG. 7 is a diagram of a cooling assembly and direct cooled packageaccording to an embodiment of the present invention.

FIGS. 8-11 are diagrams of types of spring contacts that can be used ina cooled package according to a further feature of the presentinvention. FIGS. 8A and 8B illustrate examples of wire bond springcontacts. FIGS. 9A, 9B, 10A-10C and 11 illustrate examples oflithographic spring contacts.

DETAILED DESCRIPTION OF THE INVENTION Table of Contents 1. Overview andDiscussion 2. Terminology 3. Routine for Direct Cooling of ActiveElectronic Components 4. Cooling Assembly

5. Cooled Package with One or More Dies

6. High-Density Cooled Packages

7. Cooled Package with Heat Radiator

8. Types of Spring Contacts 9. Conclusion

The following description is for the best modes presently contemplatedfor practicing the invention. This description is not to be taken in alimiting sense, but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe ascertained with reference to the claims. In the description of theinvention that follows, like numerals or reference designators will beused to refer to like parts or elements throughout.

1. OVERVIEW AND DISCUSSION

The present invention provides a cooling assembly. The cooling assemblyincludes a cooled package with one or more dies. Each die is directlycooled on one or more sides by a coolant present within the cooledpackage. Embodiments of the present invention are described with respectto a cooled high-density package. The present invention can include butis not limited to a cooled high-density package. In general, a cooledpackage according to the present invention can include only one die or aplurality of dies arranged in any configuration or layout within thecooled package.

The present invention is described in terms of an electronic packagingenvironment. Description in these terms is provided for convenienceonly. It is not intended that the invention be limited to application ofthese example environments. In fact, after reading the followingdescription, it will become apparent to a person skilled in the relevantart how to implement the invention in alternative environments known nowor developed in the future.

2. TERMINOLOGY

To more clearly delineate the present invention, an effort is madethroughout the specification to adhere to the following term definitionsas consistently as possible.

The term “die” refers to any integrated circuit, chip, silicon chip orother semiconductor or electronic device.

The terms “interconnect” and “interconnection element” refer to anyelectrical connection, including but not limited to a compliantinterconnect.

The term “compliant interconnect” refers to a non-rigid electricalconnection including, but not limited to, a spring contact availablefrom FormFactor, Inc. and the types of spring contacts described herein.

The term “active electronic component” refers to any heat generatingelectronic component including but not limited to a transistor, switch,resistor, logic gate, or integrated circuit.

The term “direct cooling of an active electronic component” as used todescribe the present invention refers to influencing the temperature ofan active electronic component with a coolant placed in thermal contactwith the active electronic component.

The term “attached” as used herein refers to any type of direct orindirect coupling.

3. ROUTINE FOR DIRECT COOLING OF ACTIVE ELECTRONIC COMPONENTS

FIG. 1 is a flowchart of a routine 100 for direct cooling of activeelectronic components according to an embodiment of the presentinvention. (Steps 110-130). In step 110, active electronic componentsare attached to a package with an active surface facing an interiorsurface of the package. The active electronic components can be directlyor indirectly coupled to the package. In embodiments, one or more dieswith active electronic components are coupled through interconnectionelements to a substrate such that the active electronic components facethe substrate. A socket configuration can also be used to hold one ormore dies relative to the substrate such that the active electroniccomponents face the substrate. In one example, the attaching stepinvolves coupling each die to a substrate through one or more compliantinterconnects.

In step 120, the attached active electronic components are sealed in thepackage. In step 130, a coolant is circulated through the package todirectly contact the active surfaces of the active electroniccomponents.

4. COOLING ASSEMBLY

FIG. 2 is a diagram of a cooling assembly 200 according to the presentinvention. Cooling assembly 200 includes cooled package 210, coolantcirculation system 212, and cooling system 214. One or more electricalinterconnections 205 and 215 are coupled to cooled package 210.Electrical interconnections 205 and 215 carry signals to and from activeelectronic components within cooled package 210. Electricalinterconnections 205 and 215 can be any type of electricalinterconnection including but not limited to compliant interconnects.Electrical interconnection 205 is shown extending from the bottom ofcooled package 210. Electrical interconnection 215 is shown extendingfrom the top of cooled package 210. Contacts (not shown) are provided onan exterior surface of a housing 216 to couple interconnections 205, 215to the cooled package 210. These are example placements only and notintended to limit the present invention. Electrical interconnections 205and 215 can also be placed in a variety of locations around cooledpackage 210 depending upon a desired configuration. Any type of contactfor a cooled package can be used including, but not limited to, bumps,pads, solder columns, contact elements, land grid array (LGA) pattern,etc. Example output contacts are further described with respect tointerconnection elements used in the high-density cooled packages ofFIGS. 4-6.

Cooled package 210 is a package that includes one or more dies 262. Eachdie 262 has one or more active electronic components. The activecomponents are arranged on an active surface of a die or in layers nearthe active surface depending the particular construction of the die. Thepackage includes a housing 216 that encloses a cavity 218. In certainembodiments, only one die or a plurality of dies 262 are arranged withinthe cavity. In other embodiments, cooled package 210 is a high-densitypackage with a plurality of dies arranged in a compact configuration.Examples of cooled packages having one or more dies are described belowwith respect to FIGS. 3A-3C and 7. Further examples of cooledhigh-density packages according to the present invention are describedbelow with respect to FIGS. 4-6.

The housing of cooled package 210 further includes at least one coolantport 220 coupled to the coolant circulation system 212. Coolant isintroduced into cavity 218 as shown by the directional arrow 222 anddirectly contacts active electronic components. Active electroniccomponents can be positioned at or near one or more surfaces of a die sothat heat is transferred from the surfaces to the coolant. Coolantcirculates throughout cavity 218 and exits at a second coolant port 224as shown by directional arrow 226. Moreover, in embodiments, the coolantcan directly contact most or all of a surface area on one or more sidesof a die. In this way, hot spots and thermal gradients are reduced oreliminated.

Cooling system 214 is coupled through coolant circulation system 212 tothe coolant ports 220, 224 of cooled package 210. Coolant circulationsystem 212 can be any type of pipe or conduit for carrying coolant toand from cooled package 210 and cooling system 214. Cooling system 214is any type of conventional cooling system for circulating coolant andtransferring heat. Multiple ports and mechanical devices can be used toevenly distribute coolant within a cavity or to distribute coolant in aparticular way. In one example, a tank holding liquid coolant is used incooling system 214. Pumps are used to drive liquid to and from thecoolant circulation system 212. A refrigerator coil is provided in thetank to cool the coolant to a desired temperature. A heater coil canalso be added to the tank if further control of the temperature of thecoolant is desired.

Cooling system 214 can circulate any type of liquid coolant and/or gascoolant. Example types of coolant include, but are not limited to,ethylene glycol, liquified nitrogen, fluorocarbons, FLORINERT, FREON,and a combination of FREON and a nonfreezing liquid.

FIG. 3A shows another embodiment of a cooling assembly 300. Coolingassembly 300 includes a liquid coolant that boils at about the desiredoperating temperature of a die. Coolant flows through coolantcirculation system 312 at entry port 314, as shown by directional arrow316, into a housing 360 so that one or more dies 362 are immersed in theliquid coolant below a coolant level 364. During operation, each die 362may generate sufficient heat to cause microboiling near active surfacesof the die. Such microboiling converts some of the liquid coolant into agas. This provides an additional advantage in that the liquid coolantsurrounding each die 362 generally remains at a constant temperatureduring boiling. This increases the operating temperature range of eachdie. FIG. 3B is plot that illustrates the principle of how a liquidcoolant generally remains at a constant temperature during a boilingrange 370. A combination of liquid and gas (or gas only) then exitshousing 360 at exit port 318, as shown by directional arrow 320, andtravels through coolant circulation system 312 to liquifier 352.Liquifier 352 converts the coolant from a gas phase back into a liquidphase before pumping or circulating the coolant back into housing 360.

Electrical interconnections 205, 215 are coupled to housing 360 to passelectrical signals in and out of the housing 360 and each die 362.Electrical interconnection 205 is shown extending from the bottom ofhousing 360. Electrical interconnection 215 is shown extending from thetop of housing 360. Contacts (not shown) are provided on housing 360 tocouple interconnections 205, 215 to housing 360. These are exampleplacements only and not intended to limit the present invention. Anumber of electrical interconnections 205 and 215 can also be placed ina variety of locations around housing 360 depending upon a desiredconfiguration.

Examples of cooled packages are now described in further detail withrespect to FIGS. 3C-7. These examples are illustrative and not intendedto limit the present invention.

5. COOLED PACKAGE WITH ONE OR MORE DIES

FIG. 3C is a diagram of a cooled package 380 according to a furtherembodiment of the present invention. Cooled package 380 includes ahousing made up of a chamber 381 and bottom substrate 382. Chamber 381can be made from ceramic, stamped metal, molded plastic, cast metal,etc. Bottom substrate 382 can be any type of substrate including, butnot limited to, a substrate made of FR-4, ceramic, copper-invar-copper,etc.

One or dies 362 are coupled to a surface of bottom substrate 382 withina cavity 383 in chamber 381. One die 362 may be used as shown in FIG.3C. Alternatively, a plurality of dies 362 may be used. Die(s) 362 canbe arranged in any desired layout on the surface of the bottom substrate382. Each die 362 is coupled to bottom substrate 382 through respectiveinterconnects 388. Interconnects 388 can be any type of electricalinterconnection element including, but not limited to, compliantinterconnects. Examples of compliant interconnects are further describedbelow. In one preferred embodiment, each die 362 is coupled to bottomsubstrate 382 through respective groups of compliant interconnects 388.Die(s) 362 are further mounted such that an active surface 385 of a die362 faces toward an inside surface of bottom substrate 382.

In FIG. 3C, two coolant ports 384, 386 are shown. Coolant port 384allows coolant to pass into chamber 381 as shown by directional arrow390. Coolant port 386 allows coolant within chamber 381 to exit as shownby directional arrow 392. In one example, coolant ports 384, 386 areone-way fluid flow valves. In other examples, one port or many ports ofany type can be used. Such ports and/or other mechanical devices canpermit a one-way or two-way flow of coolant.

Within a cavity in chamber 381, the coolant freely circulates around allsides of die(s) 362 and interconnects 388. The coolant directly coolsactive electronic components on die(s) 362. In this way, the presentinvention reduces the magnitude of thermal gradients across each die andmakes remaining thermal gradients (if any) more even across each die.Hot spots are reduced or eliminated.

Electrical interconnections 205, 215 pass electrical signals in and outof chamber 381 and each die 362. Electrical interconnection 205 is shownextending from the bottom of substrate 382. Electrical interconnection215 is shown extending from the top of chamber 381. Contacts (not shown)are provided on substrate 382 to couple interconnections 205 to thesubstrate. Contacts (not shown) are also provided on chamber 381 tocouple interconnections 215 to the chamber. These are example placementsonly and not intended to limit the present invention. A number ofelectrical interconnections 205 and 215 (and associated contacts) canalso be placed in a variety of locations depending upon a desiredconfiguration.

6. HIGH-DENSITY COOLED PACKAGES

FIG. 4A is a diagram of a high-density cooled package 400 according toan embodiment of the present invention. High density cooled package 400includes a housing made up of a bottom ceramic substrate 410 and topceramic substrate 420. Top and bottom ceramic substrates 410 and 420 aresealed by a seal 440 and enclose a cavity 402. Seal 440 can be any typeof seal that can retain a coolant. In one example, seal 440 is anO-ring.

An array of dies 430 a-430 c are coupled to a surface of bottom ceramicsubstrate 410 within cavity 402. Any number of dies 430 may be used tocover the available surface area (also called package component area) onthe surface of the bottom ceramic substrate 410 within cavity 402. Inone embodiment, sixty-four dies are provided in a densely packed,multi-chip arrangement.

In one preferred embodiment, each of the dies 430 a-430 c are coupled tothe bottom ceramic substrate 410 through respective compliantinterconnects 432 a-432 c. Dies 430 are further mounted to face bottomceramic substrate 410. In particular, an active surface of the die 430 afaces bottom ceramic substrate 410. Active surfaces of other dies 430b-430 c similarly face bottom ceramic substrate 410.

In FIG. 4A, two coolant ports 442, 444 are shown. Coolant port 442allows coolant to pass into cavity 402. Coolant port 444 allows coolantto exit cavity 402. In one example, coolant ports 442 and 444 areone-way fluid flow valves. Within cavity 402, the coolant freelycirculates around all sides of dies 430 and compliant interconnects 432.The coolant directly cools active electronic components on dies 430. Inthis way, the present invention reduces the magnitude of thermalgradients across each die and makes remaining thermal gradients moreeven across each die. Hot spots are reduced or eliminated. By minimizingtemperature variation across the die with direct cooling, high-densitypackage 400 reduces electrical parameter variation and parasitics, andprovides an improved uniformity of output signal characteristics such asrise time and pin-to-pin skew.

High-density package 400 includes interconnections 205 coupled to abottom surface of bottom ceramic substrate 410. Interconnections 205 canpass signals into package 400. High-density package 400 also hascontacts 413 provided on an edge region of the bottom ceramic substrate410. Contacts 413 are electrically coupled to interconnection elements415. In one example, output contacts 413 can be a land grid array (LGA)pattern. Interconnection elements 415 can be any type of electricalinterconnection element, including but not limited to compliantinterconnects. Interconnects 415 are further coupled to pass signalsfrom dies 430 out of package 400 to any external component. For example,interconnects 415 can be coupled to an interposer, printed circuitboard, computer, processor, or other external component.

FIG. 4B is a diagram that shows dies 430 a, 430 b mounted in a stackeddie arrangement according to an embodiment of the present invention.Dies 430 a, 430 b are flip-chip bonded to top substrate 420. Topsubstrate 420 is then coupled by compliant interconnects 482 to bottomsubstrate 410. This stacked die arrangement can be implemented in any ofthe cooled packages described herein including but not limited tohigh-density cooled packages. Coolant circulates around dies 430 a, 430b to directly cool die surfaces.

FIG. 4C is a diagram that illustrates non-contacting compliantinterconnects 494 provided on a die surface 430 a according to a furtherfeature of the present invention. Coolant circulates around die 430 a,compliant interconnects 432 a, and non-contacting compliantinterconnects 494 to directly cool die surfaces. Non-contactingcompliant interconnects 494 can be any type of compliant interconnectsuch as a spring. As shown in FIG. 4C, non-contacting compliantinterconnects 494 do not contact bottom substrate 410, but serve todirect heat away from areas of the die surface. This further improvescooling of die(s) in a cooled package according to the presentinvention. This arrangement of one or more dies with non-contactingcompliant interconnects can be implemented in any of the cooled packagesdescribed herein including but not limited to high-density cooledpackages.

FIG. 5 is a diagram of a high-density package according to a furtherembodiment of the present invention. High-density package 500 includes ahousing that encloses a cavity 502. The housing includes a bottomceramic substrate 510 and top ceramic substrate 520. Top and bottomceramic substrates 510 and 520 are coupled in a sealed package by seal440. Coolant ports 442 and 444 allow the circulation of a liquid coolantthrough cavity 502, as described above with respect to FIG. 4A. Bottomceramic substrate 510 is coupled on one surface to interconnectionelements 205. Another surface of bottom ceramic substrate 510 is coupledto dies 430 through compliant interconnects 432.

Unlike package 400, package 500 includes output contacts 513 provided ona top surface 521 of top ceramic substrate 520. Output contacts 513, forexample, can be a LGA pattern. Also, interconnections 515 are providedthrough cavity 502 between top and bottom ceramic substrates 510, 520. Anumber of interconnections 515 can be provided as desired. Package 500has all the advantages described above with respect to package 400, inthat the thermal gradients in dies 430 are reduced. Package 500 is evenmore compact, in that the output contacts do not have to be provided onan edge region of the bottom ceramic substrate 510. Instead, outputcontacts 513 are provided on the top surface 521 of top ceramicsubstrate 520. In this way, electrical signals can pass through outputcontacts 513 to any external components.

FIG. 6 is a diagram of a high-density package 600 according to a furtherembodiment of the present invention. High-density package 600 isidentical to package 500, except that the dies 430 are coupled to bottomceramic substrate 510 in a socket configuration. Die alignment posts670,672 are provided for each die 430. In FIG. 6, die alignment posts670 a,672 a are provided on opposite sides of die 430 a. Die 430 a isheld by frictional contact with die alignment posts 670 a and 672 a, andby compliant interconnections 432 a and 680 a, to maintain its position.In particular, compliant interconnections 680 a provide a downwardpressure to hold dies 430s in place in the sockets. Coolant providedwithin cavity 502 is still able to circulate on exposed sides of the die430. Even though FIG. 6 shows a socket configuration of dies withrespect to the high-density package 500, the present invention is not solimited. In particular, a socket configuration can also be used in anycooled package having any number of dies or any layout of dies byproviding die alignment posts. Output contacts 513, shown in FIG. 6 asLGA pattern 660, are provided on the top surface 521 of ceramicsubstrate 520. Compliant interconnects 662 permit connection to externalcomponents, but it should be understood that other types ofinterconnection elements may be used.

7. COOLED PACKAGE WITH HEAT RADIATOR

As shown in a side view in FIG. 7, in another embodiment of the presentinvention, a cooling assembly 700 includes a cooling member 720 and acooled package with one or more heat radiators 710 such as cooling fins712 a-712 e. The cooled package includes a chamber 781 that encloses acavity 705. Liquid or gas coolant is added through a valve 702 to fillcavity 705 and immerse one or more dies 362 located on substrate 382.During operation, die(s) 362 are directly cooled by surrounding coolant.Heat is transferred away from the coolant by the one or more heatradiators 710 to the cooling member 720. Cooling member 720 includes aliquid or gas coolant that circulates through cooling member 720 tofurther remove heat.

8. TYPES OF SPRING CONTACTS

According to a further feature of the present invention, spring contactsare used within a cooled package to couple one or more dies to asubstrate. Such spring contacts have an advantage in that they allowcoolant to flow around all sides of a die and around the spring contactsthemselves without impairing electrical connection between the die andthe substrate. The spring contacts are not completely rigid and canmaintain their physical integrity in the presence of circulatingcoolant. Also, the spring contacts can enhance direct cooling as theyhave a length that allows coolant circulation and thermal transfer awayfrom an active surface of a die even if the die is mounted to face asubstrate. Spring contacts are also fairly strong by themselves and donot require the use of epoxy or other material which would reduce thesurface area on a die which is directly cooled by circulating coolant.

Any type of spring contact can be used in a cooled package according toa further feature of the present invention. A spring contact (alsoreferred to as a compliant interconnect, contact spring or spring) caninclude, but is not limited to, any spring contact available now or inthe future from FormFactor, Inc. a Delaware corporation. For example,three types of example spring contacts that can be used in a cooledpackage according to the present invention are wirebond, multipartlithographic, and integrally formed springs.

FIGS. 8-11 are diagrams of three types of example spring contacts thatcan be used in a cooled package. The first type is a wirebond springcontact. FIG. 8A illustrates an exemplary conductive spring contact 810that may be secured to an input/output terminal 804 on a substrate 802.The exemplary spring contact 810 comprises an inner core 830 made of areadily shapeable material and a coating material 832 made of aresilient material. The spring contact 810 is preferably made by wirebonding the inner core 830 to the input/output terminal 804. Because theinner core 830 is made of a readily shapeable material, the inner coremay be formed in just about any shape imaginable, including withoutlimitation shapes having a bend or change of direction as illustrated inFIG. 8B, and shapes having multiple changes in direction. Then, thecoating material 832 is applied over the inner core 830. The coatingmaterial 832 gives the spring contact 810 resiliency. Many variations ofthe spring 810 are possible. For example, additional layers of materialsmay be added to the spring contact for a variety of purposes.

FIG. 8B shows an example spring 810′ having two bends. Spring 810′includes an inner core 830′ made of a readily shapeable material and acoating material 832′ made of a resilient material. Spring contact 810′is preferably made by wire bonding the inner core 830′ to theinput/output terminal 804′. Then, the coating material 832′ is appliedover the inner core 830′. Further details regarding the construction ofspring contacts are described in commonly-assigned U.S. Pat. Nos.5,476,211, 5,917,707, and 6,110,823, each of which is incorporatedherein in its entirety by reference.

FIGS. 9A, 9B, 10A-10C and 11 illustrate spring contacts that are madewith lithographic techniques. Such spring contacts are made usinglithographic techniques similar to techniques used for making integratedcircuits. That is, one or more masking layers are used to create apattern in which elements of the spring contact are formed. FIGS. 9A and9B illustrate an example in which a contact spring is formedlithographically. As shown one or more masking layers 930 are formed ona substrate 902. Masking layers 930 form an opening over an input/outputterminal 904 of substrate 902 and also define a shape of the springcontact. Material 940 is then deposited on the pattern formed by themasking layers 930. As shown in FIG. 9B, the masking layers are thenremoved, leaving a spring contact 910 that is secured to theinput/output terminal 904. The spring may be made of a single, springymaterial. Alternatively, the spring may be made of multiple layers ofmaterials. For example, the initial material 940 deposited in themasking layers 930 may be a flexible material such as forms the innercore of the springs illustrated in FIGS. 8A and 8B. That material maythen be coated, for example, after the masking layers are removed, witha resilient material as described above with regard to FIGS. 8A and 8B.

The shapes and configurations of contact springs formed lithographicallyare almost limitless. FIGS. 10A-10C and 11 illustrate nonexclusiveexamples of such shapes and configurations. In FIG. 10A, a plurality ofmasking layers 1032, 1034, 1036 define a spring shape at an input/outputterminal 1004. As shown in FIGS. 10B and 10C, depositing a springmaterial or materials 1040 on the masking layers and then removing themasking layers forms a spring 1010 having a base portion 1050 secured tothe input/output terminal 1004, a beam portion 1052, and a contactportion 1054.

FIG. 11 illustrates an example of a multi-part lithographically formedspring contact 1110 in which distinct post 1122, beam 1124, and tip 1126portions are created. Typically, the post 1122 is created by forming afirst masking layer (not shown) over a substrate 1102 with an openingover an input/output terminal 1104 defining post 1122. The opening isthen filled, forming the post 1122. Thereafter, a second masking layer(not shown) is formed over the first masking layer, defining an openingthat includes the post 1122 and defines the beam 1124. The beam 1124 isthen created by filling the opening with a material. The process is thenrepeated with a third masking layer (not shown) defining the tip 1126.

It should be noted that, rather than form springs on the substrate,springs may be formed separately from the substrate and, once formed,attached to the substrate. Further and more detailed descriptions oflithographically formed spring contacts may be found incommonly-assigned U.S. patent application Ser. No. 09/032,473, filedFeb. 26, 1998 (PCT publication WO 9852224), U.S. patent application Ser.No. 09/205,023, filed Dec. 2, 1998, and U.S. Pat. No. 6,255,126, allthree of which are incorporated by reference herein in their entirety.

These spring contacts are illustrative examples of compliantinterconnection elements and not intended to limit the presentinvention. Any interconnection element including, but not limited to,compliant interconnection elements may be used to couple one or moredies within a cooled package in a cooling assembly according to thepresent invention.

9. CONCLUSION

The previous description of the preferred embodiments is provided toenable any person skilled in the art to make or use the presentinvention. While the invention has been particularly shown and describedwith reference to preferred embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention.

1: A cooling assembly comprising: an electronic package having a cavity;at least one die with active electronic components located in thecavity; and at least one coolant port that allows a coolant to enter thecavity and directly cool the active electronic components of each die.2-28. (canceled)